Acids and Bases (Chapter 19): Properties of acids: Taste sour React with metals to form hydrogen gas React with carbonates to form CO 2 gas Form electrolyte solutions Turn blue litmus red Properties of bases: Feel slippery Taste bitter Will react with some metals Form electrolyte solutions Turn red litmus blue

pH scale 0714acidicbasic [H + ] > [OH - ][H + ] < [OH - ][H + ] = [OH - ] Calculating pH: Ex 1: What is the pH of a 0.15 M solution of HCl? pH = -log(0.15) = 0.82 pH = -log[H + ]pOH = -log[OH-] pH + pOH = 14 Ex 2: What is the pH of a 0.15M solution of NaOH? pOH = -log(0.15) = 0.82pH = 14 – 0.82 = 13.18

Arrhenius model of acids and bases: An acid contains acidic protons that will ionize in water to form hydrogen ions. HCl (aq)  H + (aq) + Cl - (aq) A base contains hydroxide ions that will ionize in water and produce aqueous hydroxide ions. NaOH (s)  Na + (aq) + OH - (aq) H 2 SO 4 (aq)  2 H + (aq) + SO 4 2- (aq) pH of 0.1M soln? pH = -log(0.1) = 1 pH = -log(0.2) = 0.7 pH of 0.1M soln? pH = 14 - pOH pH = 14 + log(0.1) = 13 Mg(OH) 2 (s)  Mg 2+ (aq) + 2 OH - (aq)pH = 14 + log(0.2) = 13.3

Brønsted-Lowry model of acids and bases: Acids increase the hydrogen ion concentration in a solution by donating a hydrogen ion. Bases increase the hydroxide ion concentration in a solution by accepting a hydrogen-ion. HX (aq) + H 2 O (l) ⇋ H 3 O + (aq) + X - (aq) Acid H + donor Conjugate acid H + donor Base H + acceptor Conjugate base H + acceptor

Another example: NH 3 (aq) + H 2 O (l) ⇋ NH 4 + (aq) + OH - (aq) acidbaseConjugate acid Conjugate base Substances that can act as either an acid or a base (e.g. H 2 O) are called amphoteric.

Naming Acids Binary acids: contain hydrogen and one other element 1.First part of name is hydro- 2.Second part is the root of the second element with the suffix –ic Ex: HCl is hydrochloric acid Oxyacids: acid form of a polyatomic anion that contains oxygen Format: Root of anion + suffix acid Suffixes: -ate  -ic-ite  -ous HNO 3 Nitric acid HNO 2 Nitrous acid

HC 2 H 3 O 2 HNO 3 H 2 CO 3 HCl H 3 PO 4 H 2 SO 4 H 2 S The hydrogens that appear first in the formula are called ACIDIC PROTONS, or just PROTONS for short. Monoprotic acid:an acid with only one acidic proton Polyprotic acid: an acid with more than one acidic proton (diprotic = 2, triprotic = 3) Acetic acid (vinegar) Nitric acid (acid rain) Carbonic acid (in sodas) Hydrochloric acid (stomach acid) Phosphoric acid (in colas) Sulfuric acid (battery acid) Hydrosulfuric acid (rotten egg smelling toxin) Acid nameAcid examples:

Ionization of polyprotic acids proceeds stepwise: First ionization: H 3 PO 4 (aq) ⇋ H 2 PO 4 - (aq) + H + (aq) Second ionization: H 2 PO 4 - (aq) ⇋ HPO 4 -2 (aq) + H + (aq) Third ionization: HPO 4 -2 (aq) ⇋ PO 4 -3 (aq) + H + (aq) Anhydrides: oxides that can act like acids or bases in water by reacting with the water. CaO (s) + H 2 O (l) ⇋ Ca 2+ (aq) + 2OH - (aq) CO 2 (g) + H 2 O (l) ⇋ H 2 CO 3 (aq) ⇋ H + (aq) + HCO 3 - (aq)

Indicators: organic dyes whose color depends upon the pH of the solution.

Acid-Base reactions The H + from the acid reacts with the OH -1 from the base to form water. H + + OH - H2OH2O This is called areaction

Examples: What would the products be if HCl and NaOH reacted? HCl + NaOHH 2 O +NaCl If HCl and KOH reacted? HCl + KOHH 2 O +KCl If HCl and Mg(OH) 2 reacted? HCl + Mg(OH) 2 H 2 O +MgCl 2 2 2

In general... *A salt is any ionic compound that is NOT an acid or a base.